How much of the Netherlands is affected by the problem regulated by the Hoogheemraadschap van Rijnland? 
two thirds of its area
-1
Section::::Abstract.
Hoogheemraadschap van Rijnland
29081251
-1
Section::::Abstract.
Hoogheemraadschap van Rijnland
29081251
-1
Section::::Abstract.
Flood control in the Netherlands
4865141